THE CAUSES AND MECHANISM OF COMBUSTION 545 



or by means of enzymatic or other secretory products. This has not yet 

 been proved to be the case in living cells, for even in 'highly energetic mould- 

 fungi no power of inducing extracellular oxidation can be detected even by 

 the most delicate tests (indigo-carmin, methyl-blue, potassium iodide-starch, 

 and iron) l , and it has yet to be determined whether any such power is 

 exercised by acetic acid bacteria, or by other micro-organisms. 



The reactions given by dead cells, or by the expressed sap, form no 

 sure indication as to the conditions existing in the living cell, for in the 

 latter, substances may be kept apart which react when in contact, as for 

 example when a glucoside and a glucoside enzyme are present in the same 

 cell. Various post-mortem oxidations may occur after death, as for example 

 when the sap of Monotropa, Vicia faba, &c., turns brown 2 . These appear 

 to be produced by the action of certain substances to which the provisional 

 name of 'oxydases' may be given 3 , and from facts already mentioned it is 

 not improbable that substances may be produced which are intended to act 

 only after the death of the cell containing them. Schonbein 4 has shown 

 that expressed sap has a slight power of inducing ozonization, but it is 

 erroneous to draw any conclusions from this fact as to what occurs in the 

 living cell, for as a matter of fact no ozone is present in the latter. 

 No discussion is therefore necessary of those theories which are based 

 upon this false assumption, nor can any reasons be given for the production 

 of ozone which is frequently induced by autoxidation 5 . 



In many cases marked changes due to oxidation take place after death, and 

 these may or may not be accompanied by an evolution of carbon dioxide, which 

 latter, however, in other plants ceases at ordinary temperatures as soon as death 

 ensues 6 . Brenstein's contradictory results were due to experimental error. On the 

 evolution of carbon dioxide at 7o-iooC.. cf. Schlosing, Compt. rend., 1888, T. cvi, 

 p. 1293; 1889, T. cvm, p. 527 ; Berthelot et Andre, 1894, T. cxvin, pp. 45, 104. 



The permanent absence of ozone and of hydrogen peroxide from the living cell 

 is shown by the fact that certain oxidations are not carried out which are at once 



1 Pfeffer, Oxydationsvorgange, 1889, p. 471. 



2 Pfeffer, 1. c., pp. 430, 447. 



3 Cf. Lafar, Technische Mykologie, 1897, Bd. I, p. 357. Bertrand (Compt. rend., 1895, T. cxx, 

 p. 266; 1896, T. cxxil, p. 1215) calls the oxidizing ferment of the lac tree ' Lakkase,' and states 

 (1. c., 1897, T. CXXIV, p. 1032) that it acts only in the presence of Mn. Bouiquelot v Compt. rend., 

 1896, T. cxxni, pp. 260, 315, 463) has detected oxidizing ferments in fungi. Cf. also Griiss, Landw. 

 Jahrb., 1896, Bd. XXV, p. 388 (potato). Cf. also Sect. 91. [Raciborski (Ber. d. Bot. Ges., 1898, 

 Bd. xvi, pp. 53, 119) has found that a substance capable of inducing the oxidation of hydroxyl- 

 guiacum solution is widely distributed in many tropical plants, but whether one or more oxidases are 

 concerned in producing the blue reaction used as a test is quite uncertain, and hence the special term 

 ' leptomin' is without justification. Cf. Griiss, Ber. d. Bot. Ges., 1898, Bd. xvi, p. 129.] 



* The literature is in part given by Pfeffer, 1889, 1. c., p. 466. 



5 Cf. Pfeffer, 1. c., pp. 444, 498 ; also Nasse, Pflliger's Archiv f. Physiol., 1887, Bd. XLI, p. 380. 



6 See the literature mentioned by Pfeffer (Oxydationsvorg., 1889, p. 501), and also Kreusler 

 (Landw. Jahrb., 1890, p. 664; Clausen, ibid., 1891, p. 21). 



PFEFFER N II 



